Circuit arrangement for energizing discharge devices

ABSTRACT

15. Apparatus for supplying operating electrical energy from a source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means; electrical conductors connecting accumulated lamp and said storage means to said input terminals in an interruptible current path; when said current path is not interrupted, said lamp is operated from said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp and said storage means are connected in a closed loop to operate said lamp from electrical energy previously stored in said storage means; a sensing and control means responsive to the magnitude of current through said lamp to repetitively interrupt and then restore the continuity of said current path; and said sensing and control means controlling the time said current path is interrupted to stabilize the operation of said lamp.

United States Patent [72] Inventor John W. Wigert Berea, Ohio 211 Appl. No. 544,035

[22] Filed Apr. 20, 1966 [45] Patented Dec. 14,1971

[73] Assignee WestinghouseElectrlc Corporation Pittsburgh, Pa.

Continuation of application Ser. No. 158,359, Dec. 11, 1961. This application Apr. 20, 1966, Ser. No. 544,035

[54] CIRCUIT ARRANGEMENT FOR ENERGIZING DISCHARGE DEVICES 18 Claims, 10 Drawing Figs.

[52] U.S.Cl 315/151, 315/151 [51] Int.Cl 1-101j61/00 [50] Field oiSearch 315/151,

[56] References Cited UNITED STATES PATENTS 3,265,930 9/1966 Powe1l...,

3,222,572 12/1965 Powell .1

Primary Examiner-John W. I-luckert Assistant Examiner-E. Wojciechowicz Attorneys-A. T. Stratton, W. D. Palmer and D. S. Buleza CLAIM: 15. Apparatus for supplying operating electrical energy from a source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means; electrical conductors connecting accumulated lamp and said storage means to said input terminals in an interruptible current path; when said current path is not interrupted, said lamp is operated from said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp and said storage means are connected in a closed loop to operate said lamp from electrical energy previously stored in said storage means; a sensing and control means responsive to the magnitude of current through said lamp to repetitively interrupt and then restore the continuity of said current path; and said sensing and control means controlling the time said current path is interrupted to stabilize the operation of said lamp.

106 OSCILLATOR; 94%

Muted es. 1%, 1971 3 3 Sheets-Sheet l CONTROL cmcun' Fig.5.

537 Q m-H 22 46 33- SENSING CONTROL 54 cmcurr Fig.2.

&4 Q 70 76 46 fi- SENSING E AND #63 CONTROL 5.,42 CIRCUIT Fig.3

WITNESSES: INVENTOR g 3 John W. wlgeri ATTORNEY I06 OSCI LLATOR 94% 3 Sheets-Sheet 2 Patmnted Dec. 14, 197T TIME .Mwmmmo 22 ,IZG 628 OSCILLATOR muted 1' 14, 11 13 5 Sheets-Sheet 3 OSCILLATOR '06 VARIABLE I94 DIRECT CURRENT CIRCUIT ARRANGEMENT FOR ENERGIZING DISCHARGE DEVICES This application is a continuation of applicationSer. No. 158,359, filed Dec. ll, l96l and owned by the present as signee.

The present invention relates to circuit arrangements for energizing load or discharge devices, such as mercury or fluorescent lamps, and more particularly to circuit arrangements which are so formed as to produce and to ballast a unidirectional current through such devices.

Where it is determined that advantageous can be derived by energizing a load or discharge device through the use of rectified alternating current from a systems standpoint, or in some instances through the use of available direct current, economic operation can be accomplished only if energy losses incurred in delivering the unidirectional current to the device are held acceptably low. For example it is well known that negative resistance discharge devices characteristically require current-limiting means. Further, a serial reactive impedance may properly provide the current-limiting function when alternating current is used to energize a discharge device, but, when unidirectional current is employed, the use of serial resistive impedance to obtain the current-limiting function is not practical because of the high energy losses incurred in transmittal.

Thus, in a circuit arranged to energize a load or discharge device with unidirectional current, the current-limiting function must be obtained efficiently or by means which introduce only negligible transmittal losses during the circuit operation. In fact, as will become evident hereafter, net advantages, for example in efficiency and weight, can actually be gained through the use of such a circuit. Where it is desired to provide other circuit functions in addition to the basic one just considered and in addition to any functions incident to this basic one, then generally such additional functions may be provided but desirably only if the basic current-limiting function is not, as a consequence, materially impaired.

It is therefore an object of the invention to provide a novel circuit arrangement for energizing a load or a discharge device with unidirectional current and for limiting or ballasting that current.

A further object of the invention is to provide a novel circuit arrangement which rectifies the current of an alternating source to energize a load or discharge device with unidirectional current and which limits or ballasts the latter current.

An additional object of this invention is to provide a novel circuit arrangement which both rectifies the current of an alternating source and controls the conduction angle of that current to energize a load or discharge device with unidirectional current.

It is another object of the invention to provide a circuit arrangement as described in the first object, with control being provided for varying the limit value of the current in order to vary the energization of the load. More specifically it is an object of the invention to provide variable ballasting of a negative resistance load so as, for example, to provide control of light output from fluorescent or mercury lamps.

It is an additional object of the invention to provide a circuit arrangement as described in the first object, in which means are provided for limiting the rate of rise of current in the load when the current tends to fluctuate.

These and other objects of the invention will become more apparent upon consideration of the following detailed description along with the attached drawings, in which:

FIG. I is a schematic diagram ofa circuit arrangement provided for energizing a load in accordance with the principles of the invention;

FIG. 2 is a schematic diagram of another circuit arrangement so provided;

FIG. 3 is a schematic diagram of still another circuit arrangement so provided;

FIG. 4 is a schematic diagram of a circuit arrangement similar to the one shown in FIG. 1, with certain circuit elements being shown in greater detail;

FIG. 5 illustrates the waveform of the supply current to the circuit arrangement of FIG. 4;

FIG. 6 is a schematic diagram of a portion of a circuit formed in accordance with the principles of the invention and illustrating the manner in which the rate of rise of load current can be limited;

FIG. 7 illustrates the waveform of the supply current to the circuit of FIG. 10;

FIG. 8 is a schematic diagram of another circuit arranged in accordance with the principles of the invention;

FIG. 9 is a schematic diagram of another circuit arranged in accordance with the principles of the invention, with means being provided for controlling the limit value of the load current; and

FIG. 10 is a schematic diagram of still another circuit arranged in accordance with the principles of the invention to produce control of the condition angle of the supply current and to enable the limit value of the load current to be controlled or varied.

In accordance with the broad precepts of the invention, a circuit arrangement comprises both means for rectifying alter nating current with the resulting direct current being delivered to a load or discharge device and an energy storage element, such as a capacitor.

Current can also be delivered from the latter element to the load or discharge device in the interest of stabilizing the energization process. Whenever the current through the discharge device exceeds a predetermined level, current-limiting or ballasting means respond to interrupt or decrease the supply of energy to the device and then the energy storage element, if circuit conditions so warrant, proceeds to continue energizing the device until the supply energy is again reactivated or increased. In addition, the ballasting means can be so provided as to vary the load current level at which the interruption or reduction of load energization occurs, and where the device is a lamp this variance forms the basis of timing control. Means can also be provided for preventing undesirable or excessive rates of load current rise, for example through the use of reac' tive impedance in a path which is serial to the load or discharge device. In those applications where a direct current source is already available, the rectifying means previously noted may be omitted.

With reference now to FIG. I, there is shown a circuit arrangement 20 having means including a sensing and control circuit 22 for limiting or ballasting load or outgoing current, In this case, an alternating current source (not shown) is provided for connection to input terminals 24 and 26. A diode or rectifier 28 (which, if desired, may be omitted in some embodiments of the invention as will appear subsequently) is included serially in a current path 30 to a load or discharge device 32 for the purpose of producing half-wave rectification and resulting unidirectional current through the device 32.

For reasons including the fact that it is desirable to provide a tendency toward constant constant current in or through the device 32, an energy storage element or a capacitor 33 is connected between the current path 30 and another current path 34 which provides for current return from the device 32 to the tenninal 26. When the current through the device 32 exceeds a predetermined level, the sensing and control circuit 22 responds to interrupt the current path 34, for example between terminals 36 and 38.

In this manner, notwithstanding the resulting interruption of the supply path between the terminals 24 and 26, current continues to energize the device 32 through the local current loop including the capacitor 33 and the device 32, with the current being produced by a discharge of the capacitor 33. When the current through the device 32 decreases to a level below the predetermined limit level, the sensing and control circuit 22 responds to cause the current path 34 once again to be continuous thereby enabling the capacitor 33 to be energized again and also enabling the discharge device 32 to be energized further directly from the terminals 24 and 26.

In FIG. 2, there is illustrated another circuit arrangement 40 in which functions similar to those provided in the circuit ar' rangement of FIG. 1 are provided and in which full rectification of the supply current is provided as well. Thus, a fullwave rectifier 42 is included in the circuit arrangement 40 to provide both for unidirectional flow of current through the device 32 and for unidirectional application of voltage across the capacitor 33. Accordingly, current from the terminal 24, being interruptable between terminals 44 and 46 or 56 and 54 of the sensing and control circuit 22, flows serially through paths 47, 48 and 50, through a path 52 and the discharge device 32 to return to terminal 26 through paths 53 and 55. Similarly, current from the terminal 26, being interruptable between the terminals 54 and 56 or 46 and 44 of the sensing and control circuit 22, flows serially through the paths 55, 53, 50 and 52 and through the lamp 32 to return to the terminal 24 through the paths 48 and 47.

FIG. 3 illustrates another circuit arrangement 60 in which means are provided for transforming the amplitude of the voltage from the terminals 24 and 26 and in which full-wave rectifying means are also provided. Thus, a transformer 62, being of ordinary construction and having a primary winding 64 and a secondary winding 66, is connected so that the primary current can be interrupted by the sensing and control circuit 22. In this embodiment, the secondary winding 66 is provided with a centrally located tap, as indicated by the reference character 68, and is so connected relative to a pair of diodes 70 and 72 as to provide for full-wave rectification and therefore unidirectional current through the device 32.

Thus, for positive half-cycles, current is enabled to flow from a portion 74 of the secondary winding 66 through the diode 70, path 76, the device 32 and paths 78 and 80 to return to the center tap 68. Similarly, for negative half-cycles current is enabled to flow from a portion 82 of the secondary winding 66 through the diode 72 and the path 76, the device 32 and the paths 78 and 80 to return to the center tap 68. In a manner similar to that described in connection with FIG. 1, the sensing and control circuit 22 responds to excessive load current through the paths 78 and 80 to cause switching to occur between the terminals 44 and 46 or the terminals 54 and 56 in the primary circuit.

For a more specific understanding of the principles of the invention, reference is to be made now to FIG. 4. Here, a circuit arrangement 20a is shown with specific circuit elements providing one of various forms that can be used for the sensing and control circuit 22. Thus, the sensing and control circuit 22 includes means for controlling or switching the continuity of the load path 34, examplarily in the form of a controlled semiconductor rectifier 90, and means for controlling the switching action of the controlled rectifier 90, including, for, example a saturable core transformer 92.

Since the controlled rectifier 90 functions as a rectifier as well as a switch, it is clear that the diode 28 which produces half-wave rectification, may be omitted if desired, as will be considered more fully in connection with FIG. 9 where fullwave rectification is employed. The saturable transformer 92 may be provided with whatever physical form is suitable for producing the ultimate function of switching the controlled rectifier 90, but it is preferred, for reasons which follow, that it include a primary 94 being energized by fluctuating or oscillating means, or by conventional oscillator 96 and a secondary 98 being serially connected in the path 34 and a tertiary winding 100 being connected across gate terminals 102 and 104 of the controlled rectifier 90.

With normal load current flowing in the path 34, a core 106 of the transformer 92 is in a desaturated condition so that the fluctuating or oscillating signal impressed by the oscillator 96 across the primary winding 94 induces in the tertiary winding 100 a similar signal which is effective periodically to drive the controlled rectifier 90 to a conductive state. The necessary amplitude of the oscillator signal is determined by factors including the turns ratio of the primary and tertiary windings 94 and 100, the extent of flux coupling between these windings and the energy required for driving the controlled rectifier 90 into a conductive state. If the frequency of the oscillating signal is selected to be the power frequency, for example 60 cycles per second, the separate oscillator 96 may be omitted and ordinary circuitry may be employed to derive energy from the line terminals 24 and 26 for the purpose of producing this signal.

If the oscillator 96 is ,used, its output is preferably synchronized with the power frequency or provided with a substantially higher frequency to permit firing of the controlled rectifier at a relatively rapid rate. Where the oscillating signal is provided with the power frequency, it is desirable that this signal be in pulse form, with each pulse occurring at the beginning of each half-cycle of the power current for the purpose of obtaining synchronism in the switching function. Of course, if the higher frequency is employed, timing becomes negligible since driving pulses are then generated rapidly enough to ensure firing of the controlled rectifier 90 at or near the beginning of each conducting half-cycle power current.

If the load current through the path 34, and therefore the secondary winding 98, becomes excessive, additional magnetic flux is created in the core 106 to drive the latter to a saturated condition so as to isolate the tertiary winding from the oscillator signal impressed across the primary winding 94. It therefore follows that the rectifier gate terminals 102 and 104 no longer receive a drive signal and the controlled rectifier 90 accordingly switches to a nonconductive state.

ln this event, current from the source terminals 24 and 26 is blocked, but current is nevertheless enabled to flow from the capacitor 33 through the local loop including the capacitor 33 and the device 32. When this local load current diminishes to a level which enables the transformer core 106 again to be desaturated, the controlled rectifier 90 is switched into a conductive state so as to enable a renewed flow of source current. As such, energy again accumulates in the capacitor 33 while load current continues to flow through the device 32. The operation just described is repeated each time the load current exceeds the value stipulated for it.

In FIG. 5, there is shown a graphic representation of the source current through the terminals 24 and 26 of FIG. 4 as a function of time. Thus, because of the described half-wave rectification, only the positive half-cycles of current can flow, and those half-cycles having a cross-lined area actually flow while the exemplary one provided with a dotted outline is disabled from flowing because, over the time period involved, the controlled rectifier 90 is caused to become nonconductive. lf full-wave rectification is used as in FIG. 2 and FIG. 3, corresponding results are obtained.

lf it is determined that current through the discharge device 32 has a tendency to rise too rapidly, means, in this instance including an ordinary inductor 108, can be provided, as shown in FIG. 6, in series with the discharge device 32 for the purpose of increasing the damping or limiting of this effect. Thus the inductor 108 limits or ballasts the rate at which current rises in the device 32, yet it can be so designed as not to introduce undesirable resistive or other losses. Similarly, the inductor 108 can be connected to precede the capacitor 33 so as to limit the rate of rise of charging current to the latter.

Where only direct source current is available, a circuit arrangement as shown in FIG. 8 can be employed. In this case, there are provided source terminals 122 and 124, and paths 126 and 128 respectively connect the terminals 122 and 124 to the device 32. In a manner similar to the case of FIG. 1, the diode 28 is included serially in the path 126 and the capacitor 33 is shunted between the paths 126 and 128.

Means for switching the path 128, for example, a semiconductor device such as a transistor 130, are included serially in the path 128. The transformer 92 with its associated circuitry is again employed, in this instance to control the switching action of the transistor 130. A direct forward-bias voltage across an emitter 132 and a base 134 of the transistor can be obtained, if desired or necessary, through a full-wave rectifier 136 which is connected to the tertiary winding 100.

Thus, a pulse or signal coupled from the oscillator 96 to the tertiary winding 100 is rectified to provide a forward bias for the transistor 130 so as to cause the latter to acquire a conductive state. As in the case of Flg. 4, saturation of the magnetic core 106 isolates the tertiary winding 100 from the primary winding 94 to cause the transistor 130 to become nonconductive. The capacitor 33 functions here in a manner identical to that described in connection with FIG. 4.

Especially in the instance where the discharge device 32 is provided in the form of a mercury or other type lamp, it is desireable that the limit value of load or lamp current be variable. Thus, in such a case, variable dimming or brightness control can be obtained.

This function can be provided in any embodiment of the invention in a manner similar to that in a circuit arrangement 140 of FIG. 9. The circuit 140 also serves to illustrate the manner in which switching elements of the sensing and control means may be used in rectifying an alternating input current. Thus, the circuit 140 includes a bias winding 142 on the core 106, with direct current for the winding 142 being obtained from the source terminals 24 and 26 through the use ofa rectifying arrangement, in this case a full-wave rectifier 144 and a control rheostat 146.

By varying the setting of the rheostat 146, one can vary the direct current through the bias winding 142 and therefore varying the bias flux which exists in the core 106. The amount of load current (or the limit current) through the path 34 which is necessary to saturate the core 106 is therefore variable since the amount of flux which is created by the load current and which is necessary to saturate the core 106 varies as the amount ofbias or other flux which exists in the core.

For any given setting of the rheostat 146, the determined limit load current is otherwise controlled generally in the manner described in connection with FIG, 4. As already suggested however, controlled rectifiers 148 and 150, driven by control windings 149 and 151 respectively, form a part of a full-wave rectifier so as both to rectify incoming power current and to switch that current off and on in controlling the energization of the device 32.

In FIG. 10, there is illustrated another embodiment of the invention in which a circuit arrangement 160 is provided to energize the load device 32, with the phase or conduction angle of incoming alternating power current being controlled to define the level at which the energization takes place. In this example, the conduction angle can, if desired, be varied independently to provide ready variation in the controlled energization level of the device 32 or in the brightness of the device 32 if it is provided in the form of a lamp. As a matter of definition, the conduction angle of the power current is descriptive of that portion of a power half-cycle during which power current flows. Thus, in FIG. 7, the conduction angle of a fully rectified power wave is indicated by any of the crosshatched portions.

In the circuit 160, alternating power current is derived from the terminals 24 and 26 and delivered through a rectifier 162 (in this case a full-wave one) to the device 32 in unidirectional form. The capacitor 33 is employed here for reasons similar to those described in connection with FIG. 4. To provide control of the conduction angle of the power current, controlled rectifiers 164 and 166 are included in each of two separate legs of the power rectifier 162. Thus, the controlled rectifiers 164 and 166 function both to rectify the power current and to limit the power current through control of its conduction angle.

Means including a phase control network 168 are provided in the circuit 160 for controlling the conduction angle of the power current. Where circuit parameters so warrant, the network 168 includes in FIG. a stepdown transformer 170 which derives energy from the terminals 24 and 26. Current from a secondary portion 172 of the transformer 170 proceeds through a path 174 and an inductive impedance element or inductor 176, while current from another secondary portion 178 proceeds through a resistive element 180 and a path 182. The

resultant current which flows through a path 184 is the vector sum of the separate currents. Similarly, the resultant voltage across the path 184 is defined by a vector sum of the voltages around either of the two current loops.

When the resultant current flows flows from a junction 173 of the transformer secondary portions 172 and 178, it proceeds through gating terminals of the controlled rectifier 164 and through a directing diode 186 to the path 1. When the resultant current flows into the junction 173, it proceeds from the path 184, through gating terminals of the controlled rectifier 166 and a directing diode 1188 to the portions 172 and 178.

The phase relation of the voltage across the path 194 relative to the voltage across the power terminals 24 and 26 is determinative of conduction angle of the power current. This is so because the time in the power-voltage cycle at which the controlled rectifier 164 or 166 is fired is determined by the phase displacement of the voltage across the path 184. The inductance of the inductor 176 and the resistance of the resistor 180 define this phase displacement, and, more particularly, as the inductance decreases and the element 176 approaches resistive character the vector for the voltage across the path 184 approaches alignment with the vector for the voltage across the power terminals 24 and 26. Whether this alignment is one in which the two vectors are in phase or l out of phase depends upon the polarity relation of the voltages across the two windings of the transformer 170. In other applications of the invention, the network 168 may be provided in other forms, for example through the use of a capacitor (not shown) in place of the inductor 176.

Further, where the inductor 176 is disposed on a saturable core 190 and a feedback winding 192, which is serially connected with the device 32, is also disposed on the core 190, current through the device 32 can be limited or ballasted very effectively, especially under circumstances where this current tends to increase even though the conduction angle is limited as just described. Thus, the winding 192, as a sensing element, produces flux in the fore 190 in accordance with the magnitude of the current through the device 32, and, where this current is caused to become excessive by some circuit condi tion, the self-inductance of the inductor 176 is caused to decrease. Accordingly, assuming the polarities of the windings of the transformer to be such as to enable a I80 shift in the alignment of the vectors for the power voltage and the voltage across the path 184, the inductor 176 in turn causes the conduction angle of the power current to be decreased somewhat thereby to diminish the time over which the power current flows and, consequently, to diminish the excessive level of energization of the device 32. In the extreme case, the core becomes fully saturated, the inductor 176 is minimally inductive so as to produce a shift of close to I80 in the two mentioned vectors and a minimum conduction angle of the power current is thereby defined. This minimum angle, being determined by design considerations, can be made low enough in value to ensure effective ballasting.

Bias flux means for an additional winding 194, being variably energizable by suitable means (not shown), can be utilized on the core 190 to enable the controlled energization level of the device 32 to be varied. Thus, variable direct current through the winding 194 produces variable-bias flux in the core 190, either in aiding or in bucking relation to the flux produced by the winding 192, and therefore produces varia' ble-bias flux linking the inductor 176 to prescribe respectively variable limits of power current through the winding 192. If the device 32 is a lamp, dimming or brightness control is thereby effectively provided. In general, the circuit 160 tends to provide smoother control of the energization of the device 32 than do other described embodiments of the invention, since energizing current may flow during each power halfcycle in the former whereas, in the latter, current is complete ly cutoff during some half-cycles.

Where the winding 194 is in aiding relation to the winding 192, as in FIG. 10, the core 190 is normally desaturated to a degree determined by the current through the bias winding 194 and increasing load current tends to drive the core 190 toward saturation and servomechanic control is obtained in the manner already described. Where the relation is a bucking one, the core 190 is normally saturated to a degree determined by the current through the bias winding 194 and increasing load current tends to drive the core 190 out of saturation with resulting increase in the inductance of the inductor 176. To obtain servomechanic control in the latter instance, the network 168 must be so provided as to produce a decrease in the power conduction angle for increasing inductance of the inductor 176. This can be accomplished, for example, by establishing the polarities of the windings of the transformer 170 so as to enable an in-phase alignment of the vectors for the power voltage and the voltage across the path 184.

In the foregoing description, the mode of operation of several exemplary circuit arrangements has been related to point out the principles of the invention. The description, therefore, has only been illustrative of the invention, and, accordingly, it is desired that the invention be not limited by the embodiments described here but, rather, that it be accorded an interpretation consistent with the scope and spirit of its broad principles. Moreover, it is to be understood that certain features of the invention can be utilized to advantage without a corresponding use of other features thereof.

I claim as my invention:

1. A circuit having input terminal means adapted to be connected to an input current source for energizing a load device and limiting the current to the load device substantially to a predetermined value, said circuit comprising:

switching means connected between said input terminal means and the load device for controlling the input current;

signal means for providing a fluctuating signal;

a saturable core transformer having a first winding, a second winding and a third winding, said first winding connected to said signal means for establishing a fluctuating flux within the core of said transformer, said second winding connected in series with the load device and said switching means, and when current through said load device and said second winding exceeds said predetermined value the core of said transformer being saturated by the current through said second winding,

said switching means responsive to the fluctuating signal provided by said signal means to display a low-impedance state, said switching means when not signalled by the signal provided by said signal means displaying a high-impedance state; and

said first winding and said third winding coupling said switching means to said signal means when the core of said transformer is not saturated, and said first winding and said third winding being decoupled when the core of said transformer is saturated; whereby whenever the current through the load device exceeds said predetermined value, said switching means is switched to a high-impedance state to limit the current to the load device.

2. The circuit as specified in claim 1. wherein a current storage element is connected across the load device and said second winding for providing current through the load and said second winding when said switching means is in the high impedance state.

3. The circuit as specified in claim 1, wherein said transformer has a fourth winding for biasing the saturation level thereof to control the magnitude of current to the load device.

4. The circuit as specified in claim 1, wherein a rectifying means is connected between said input terminal means and the load device for providing unidirectional current for the load. 7

5. The circuit as specified in claim 1, wherein said switching means is a semiconductor device.

6. The circuit as specified in claim 1, wherein said signal means is an oscillator to provide the fluctuating signal.

7. In combination, a circuit having input terminals adapted to be connected to an input AC source, and a gaseous discharge load device having negative volt-ampere characteristics connected to the output of said circuit and energized by said circuit with an output DC which is limited substantially to a predetermined value, said circuit providing the required ballast for preventing runaway conduction in said load due to its negative volt'ampere characteristics, said circuit comprising:

switching rectifying means connected between said input terminal and said load for rectifying the AC input current and also for controlling the input current by means of a low-impedance state operable to conduct current therethrough and a high-impedance state operable to prevent flow therethrough, the low-impedance state of said switching means being at least in part determined by signals applied to the control terminals thereof;

saturable core transformer having first and second windings, said second winding connected in series with said load and operable to vary the saturation level of the core of said transformer in response to variations in the output current level, said first winding winding having an inductive impedance which is dependent on the saturation level of the core of said transformer, said first winding connected to said switching means for providing a signal thereto which is phase-displaced from the input AC due to the inductance of said first winding to provide the ballasting action by controlling the low-impedance state of said switching means in response to variations in the load current level;

and a capacitor connected across said load and said second winding for providing current to said load and said second winding when said switching means is in the high-impedance state so that as the output current varies, the conduction time of said switching means varies changing the current conducted therethrough to counter the variation in the output current which limits the current through said load to a predetermined value.

8. The circuit as specified in claim 7, wherein said transformer is provided with a third winding which is energized by DC to bias the saturation level of the core of said transformer to determine the given value about which the output current is limited.

9. The circuit as specified in claim 7, wherein said switching rectifying means is a semiconductor device.

10. An apparatus for operating an electric discharge lamp from a power source, said apparatus comprising: a power source, an electric discharge lamp, a control means for varying the energy supplied to the electric discharge lamp by the power source, a feedback circuit coupled to said lamp for providing a feedback signal indicative of a lamp operating condition and coupled with said control means to activate said control means in response to said feedback signal, and circuit means including input leads for connection to the power source and including output leads for connection with the electric discharge lamp to supply the output of the apparatus to the lamp, said circuit means connecting said control means in circuit with said output leads and said input leads, and said control means dynamically balancing the energy from the source with the energy required to control the operation of the electric discharge lamp by repetitively varying the energy supplied at said output leads from one predetermined level to another at a rate which varies as a function of the magnitude of current in said discharge lamp.

11. The apparatus set forth in claim 10 wherein said feedback circuit is connected in circuit with one of said output leads to supply a feedback signal to said control means that is functionally related to the lamp current.

12. An apparatus for operating at least one electric discharge lamp from a power source, said apparatus comprising: a power source, at least one electric discharge lamp, a control means for repetitively varying the voltage across said electric discharge lamp from one predetermined level to another, feedback circuit for providing a feedback signal indicative of a lamp-operating condition and coupled to said lamp coupled with said control means for activating said control means in response to a feedback signal indicative of a lamp-operating condition. and circuit means including input leads for connection to the power source and including output leads for connection with at least one electric discharge lamp to supply the output of the apparatus to the lamp, said circuit means connecting said control means in circuit with at least one of said output leads and one of said input leads to place said control means in series circuit relation with the lamp, and said control means dynamically balancing the voltage at the source with the voltage required to control the operation of the electric discharge lamp by repetitively varying the energy supplied at the output leads from said one predetermined level to another in response to and at a rate indicate of the magnitude of said feedback signal.

13. An apparatus for operating an electric discharge lamp, said apparatus comprising: a direct current source, an electric discharge lamp, input leads for connection to the direct current source, a pair of output leads for supplying the output of the apparatus to at least one electric discharge lamp, a switching transistor having an emitter, collector and base electrode, said emitter and collector electrodes being connected in circuit with one of said input leads and one of said output leads, circuit means connecting the other of said output leads in circuit with the other of said input leads, a driver means coupled with said switching transistor to activate said switching transistor between a highand low-impedance state to vary the impedance in circuit with the electric discharge lamp thereby causing the current supplied at the output leads to vary from one current level to another, said driver means being driven in response to a lamp operating condition and said switching transistor being repetitively activated to operate said at least one electric discharge lamp between said current levels at a rate which varies as a function of the magnitude of current in said lamp.

[4 The apparatus set forth in claim 13 wherein an impedance element is connected in series circuit relation with said switching transistor to control the rate of change of the current between said current levels.

15, Apparatus for supplying operating electric energy from a source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means; electrical conductors connecting said lamp and said storage means to said input terminals in an interruptible current path; when said current path is not interrupted. said lamp is operated from said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp and said storage means are connected in a closed loop to operate said lamp from electrical energy previously stored in said storage means; a sensing and control means responsive to the magnitude of current through said lamp to repetitively interrupt and then restore the continuity of said current path; and said sensing and control means controlling the time said current path is interrupted to stabilize the operation ofsaid lamp.

16. Apparatus for supply operating electric energy from source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means; electrical conductors connecting said lamp and said storage means to said input terminals in an interruptible current path and also connecting said lamp and said storage means in a closed loop which is parallel connected with respect to said input terminals; a sensing and control means responsive to the magnitude of current through said lamp to repetitively interrupt and then restore the continuity of said current path at a point intermediate said closed loop and said input terminals; when said current path is interrupted, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; and said sensing and control means controlling the time said current path is interrupted in accordance with the magnitude of current through. said lamp to stabilize the operation of said lamp.

17. Apparatus for supplying operating electric energy from an AC source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means comprising a capacitor; electrical conductor connecting said lamp and said storage means in a closed loop and also connecting said closed-loop connected lamp and storage means in parallel with said input terminals in a current path which is interruptible; rectifier bridge means connected across said input terminals for converting electric energy from said AC source to a rectified pulsating output; a sensing and control means including semiconductorcontrolled rectifier means in circuit with said current path in termediate said close loop and said input terminals, said semiconductor'controlled rectifier means operable to switch to nonconducting state and interrupt said current path each half-cycle of energizing potential, said sensing and control means also connecting to said closed loop and responsive to the magnitude of current through said lamp to repetitively switch said semiconductor-controlled rectifier means to a conducting state each half-cycle of energizing potential and establish the continuity of said current path between said closed loop and said input terminals; when said semiconductor-controlled rectifier means is in a conducting state, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; current-limiting inductor means connected in circuit with said input terminals and said semiconductor controlled rectifier means to limit the initial current therethrough when said semiconductor-controlled rectifier means is switched to a conducting state; and said sensing and control means controlling the time said current path is interrupted in accordance with the magnitude of current through said lamp to stabilize the operation of said lamp.

18. Apparatus for supplying operating electric energy from an AC source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to sad source; an electrical energy storage means comprising a capacitor; electrical conductors connecting said lamp and said storage means in a closed loop and also connecting said closed-loop-connected lamp and storage means in parallel with said input ter minals in a current path which is interruptible; rectifier bridge means connected across said input terminals for converting electric energy from said AC source to a rectifier pulsating output; semiconductor-controlled rectifier means associated with said rectifier bridge means for switching to a nonconducting state and interrupting said current path during each half cycle of AC energy from said source; a sensing and control means having its output connected to said semiconductorcontrolled rectifier means to control the switching of same to a conducting state, and said sensing means also connected in circuit with said closed loop and responsive to the magnitude of current through said lamp to repetitively switch said semiconductor-controlled rectifier means to a conducting state each half cycle of AC energy from said source and establish the continuity of said current path between said closed loop and said input terminals; when said semiconductor-controlled rectifier means is in a conducting state, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; current-limiting inductor means connected in circuit with said input terminals and said semiconductor-controlled rectifier means to limit the initial current therethrough when said semiconductor-controlled rectifier means is switched to a conducting state; and said sensing and control means controlling the time said current path is interrupted in 

1. A circuit having input terminal means adapted to be connected to an input current source for energizing a load device and limiting the current to the load device substantially to a predetermined value, said circuit comprising: switching means connected between said input terminal means and the load device for controlling the input current; signal means for providing a fluctuating signal; a saturable core transformer having a first winding, a second winding and a third winding, said first winding connected to said signal means for establishing a fluctuating flux within the core of said transformer, said second winding connected in series with the load device and said switching means, and when current through said load device and said second winding exceeds said predetermined value the core of said transformer being saturated by the current through said second winding, and said third winding inductively coupled to said first winding through the core of said transformer and connected to said switching means; said switching means responsive to the fluctuating signal provided by said signal means to display a low-impedance state, said switching means when not signalled by the signal provided by said signal means displaying a high-impedance state; and said first winding and said third winding coupling said switching means to said signal means when the core of said transformer is not saturated, and said first winding and said third winding being decoupled when the core of said transformer is saturated; whereby whenever the current through the load device exceeds said predetermined value, said switching means is switched to a high-impedance state to limit the current to the load device.
 1. A circuit having input terminal means adapted to be connected to an input current source for energizing a load device and limiting the current to the load device substantially to a predetermined value, said circuit comprising: switching means connected between said input terminal means and the load device for controlling the input current; signal means for providing a fluctuating signal; a saturable core transformer having a first winding, a second winding and a third winding, said first winding connected to said signal means for establishing a fluctuating flux within the core of said transformer, said second winding connected in series with the load device and said switching means, and when current through said load device and said second winding exceeds said predetermined value the core of said transformer being saturated by the current through said second winding, and said third winding inductively coupled to said first winding through the core of said transformer and connected to said switching means; said switching means responsive to the fluctuating signal provided by said signal means to display a low-impedance state, said switching means when not signalled by the signal provided by said signal means displaying a high-impedance state; and said first winding and said third winding coupling said switching means to said signal means when the core of said transformer is not saturated, and said first winding and said third winding being decoupled when the core of said transformer is saturated; whereby whenever the current through the load device exceeds said predetermined value, said switching means is switched to a high-impedance state to limit the current to the load device.
 2. The circuit as specified in claim 1, wherein a current storage element is connected across the load device and said second winding for providing current through the load and said second winding when said switching means is in the high impedance state.
 3. The circuit as specified in claim 1, wherein said transformer has a fourth winding for biasing the saturation level thereof to control the magnitude of current to the load device.
 4. The circuit as specified in claim 1, wherein a rectifying means is connected between said input terminal means and the load device for providing unidirectional current for the load.
 5. The circuit as specified in claim 1, wherein said switching means is a semiconductor device.
 6. The circuit as specified in claim 1, wherein said signal means is an oscillator to provide the fluctuating signal.
 7. In combination, a circuit having input terminals adapted to be connected to an input AC source, and a gaseous discharge load device having negative volt-ampere characteristics connected to the output of said circuit and energized by said circuit with an output DC which is limited substantially to a predetermined value, said circuit providing the required ballast for preventing runaway conduction in said load due to its negative volt-ampere characteristics, said circuit comprising: switching rectifying means connected between said input terminals and said load for rectifying the AC input current and also for controlling the input current by means of a low-impedance state operable to conduct current therethrough and a high-impedance state operable to prevent flow therethrough, the low-impedance state of said switching means being at least in part determined by signals applied to the control terminals thereof; a saturable core transformer having first and second windings, said second winding conNected in series with said load and operable to vary the saturation level of the core of said transformer in response to variations in the output current level, said first winding having an inductive impedance which is dependent on the saturation level of the core of said transformer, said first winding connected to said switching means for providing a signal thereto which is phase-displaced from the input AC due to the inductance of said first winding to provide the ballasting action by controlling the low-impedance state of said switching means in response to variations in the load current level; and a capacitor connected across said load and said second winding for providing current to said load and said second winding when said switching means is in the high-impedance state so that as the output current varies, the conduction time of said switching means varies changing the current conducted therethrough to counter the variation in the output current which limits the current through said load to a predetermined value.
 8. The circuit as specified in claim 7, wherein said transformer is provided with a third winding which is energized by DC to bias the saturation level of the core of said transformer to determine the given value about which the output current is limited.
 9. The circuit as specified in claim 7, wherein said switching rectifying means is a semiconductor device.
 10. An apparatus for operating an electric discharge lamp from a power source, said apparatus comprising: a power source, an electric discharge lamp, a control means for varying the energy supplied to the electric discharge lamp by the power source, a feedback circuit coupled to said lamp for providing a feedback signal indicative of a lamp operating condition and coupled with said control means to activate said control means in response to said feedback signal, and circuit means including input leads for connection to the power source and including output leads for connection with the electric discharge lamp to supply the output of the apparatus to the lamp, said circuit means connecting said control means in circuit with said output leads and said input leads, and said control means dynamically balancing the energy from the source with the energy required to control the operation of the electric discharge lamp by repetitively varying the energy supplied at said output leads from one predetermined level to another at a rate which varies as a function of the magnitude of current in said discharge lamp.
 11. The apparatus set forth in claim 10 wherein said feedback circuit is connected in circuit with one of said output leads to supply a feedback signal to said control means that is functionally related to the lamp current.
 12. An apparatus for operating at least one electric discharge lamp from a power source, said apparatus comprising: a power source, at least one electric discharge lamp, a control means for repetitively varying the voltage across said electric discharge lamp from one predetermined level to another, feedback circuit for providing a feedback signal indicative of a lamp-operating condition and coupled to said lamp coupled with said control means for activating said control means in response to a feedback signal indicative of a lamp-operating condition, and circuit means including input leads for connection to the power source and including output leads for connection with at least one electric discharge lamp to supply the output of the apparatus to the lamp, said circuit means connecting said control means in circuit with at least one of said output leads and one of said input leads to place said control means in series circuit relation with the lamp, and said control means dynamically balancing the voltage at the source with the voltage required to control the operation of the electric discharge lamp by repetitively varying the energy supplied at the output leads from said one predetermined level to another in response to and at a rate indicate of the magnitude of said feedback signal.
 13. An apparatus for operating an electric discharge lamp, said apparatus comprising: a direct current source, an electric discharge lamp, input leads for connection to the direct current source, a pair of output leads for supplying the output of the apparatus to at least one electric discharge lamp, a switching transistor having an emitter, collector and base electrode, said emitter and collector electrodes being connected in circuit with one of said input leads and one of said output leads, circuit means connecting the other of said output leads in circuit with the other of said input leads, a driver means coupled with said switching transistor to activate said switching transistor between a high- and low-impedance state to vary the impedance in circuit with the electric discharge lamp thereby causing the current supplied at the output leads to vary from one current level to another, said driver means being driven in response to a lamp operating condition and said switching transistor being repetitively activated to operate said at least one electric discharge lamp between said current levels at a rate which varies as a function of the magnitude of current in said lamp. 14 The apparatus set forth in claim 13 wherein an impedance element is connected in series circuit relation with said switching transistor to control the rate of change of the current between said current levels.
 16. Apparatus for supply operating electric energy from a source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means; electrical conductors connecting said lamp and said storage means to said input terminals in an interruptible current path and also connecting said lamp and said storage means in a closed loop which is parallel connected with respect to said input terminals; a sensing and control means responsive to the magnitude of current through said lamp to repetitively interrupt and then restore the continuity of said current path at a point intermediate said closed loop and said input terminals; when said current path is not interrupted, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; and said sensing and control means controlling the time said current path is interrupted in accordance with the magnitude of current through said lamp to stabilize the operation of said lamp.
 17. Apparatus for supplying operating electric energy from an AC source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means comprising a capacitor; electrical conductor connecting said lamp and said storage means in a closed loop and also connecting said closed-loop connected lamp and storage means in parallel with said input terminals in a current path which is interruptible; rEctifier bridge means connected across said input terminals for converting electric energy from said AC source to a rectified pulsating output; a sensing and control means including semiconductor-controlled rectifier means in circuit with said current path intermediate said close loop and said input terminals, said semiconductor-controlled rectifier means operable to switch to nonconducting state and interrupt said current path each half-cycle of energizing potential, said sensing and control means also connecting to said closed loop and responsive to the magnitude of current through said lamp to repetitively switch said semiconductor-controlled rectifier means to a conducting state each half-cycle of energizing potential and establish the continuity of said current path between said closed loop and said input terminals; when said semiconductor-controlled rectifier means is in a conducting state, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; current-limiting inductor means connected in circuit with said input terminals and said semiconductor controlled rectifier means to limit the initial current therethrough when said semiconductor-controlled rectifier means is switched to a conducting state; and said sensing and control means controlling the time said current path is interrupted in accordance with the magnitude of current through said lamp to stabilize the operation of said lamp.
 18. Apparatus for supplying operating electric energy from an AC source to a discharge lamp, said apparatus comprising: input terminals adapted to be connected to said source; an electrical energy storage means comprising a capacitor; electrical conductors connecting said lamp and said storage means in a closed loop and also connecting said closed-loop-connected lamp and storage means in parallel with said input terminals in a current path which is interruptible; rectifier bridge means connected across said input terminals for converting electric energy from said AC source to a rectifier pulsating output; semiconductor-controlled rectifier means associated with said rectifier bridge means for switching to a nonconducting state and interrupting said current path during each half cycle of AC energy from said source; a sensing and control means having its output connected to said semiconductor-controlled rectifier means to control the switching of same to a conducting state, and said sensing means also connected in circuit with said closed loop and responsive to the magnitude of current through said lamp to repetitively switch said semiconductor-controlled rectifier means to a conducting state each half cycle of AC energy from said source and establish the continuity of said current path between said closed loop and said input terminals; when said semiconductor-controlled rectifier means is in a conducting state, said lamp is operated by direct connection with said source and electrical energy is stored in said storage means; when said current path is interrupted, said lamp is operated in said closed loop from electrical energy previously stored in said storage means; current-limiting inductor means connected in circuit with said input terminals and said semiconductor-controlled rectifier means to limit the initial current therethrough when said semiconductor-controlled rectifier means is switched to a conducting state; and said sensing and control means controlling the time said current path is interrupted in accordance with the magnitude of current through said lamp to stabilize the operation of said lamp. 